The present invention relates to an electric vehicle control system. More particularly, it concerns an electric vehicle control system which assures safe operability of the vehicle in the case of malfunction of a microcomputer which is part of the control system.
In prior art control systems for electric vehicles, a microcomputer generally receives an accelerator signal, a key switch signal, a current detection signal, and a motor rotational signal, processes this information, and controls an electric motor. Since such systems depend on the proper functioning of the microcomputer to operate the vehicle motor, a malfunction of the microcomputer can cause a loss of control. It is obviously undesirable from a safety standpoint for the driver to be unable to control the vehicle in the event of such a microcomputer malfunction. Two prior art control systems address this problem:
1. An electric vehicle control system disclosed in Japanese Patent Laid-Open No. 58703 of 1981 provides for a logical AND operation of an acceleration switching signal from a microcomputer and an accelerator switching signal, to switch a chopper to an acceleration mode. Driving can be always switched to regeneration or coasting whenever the accelerator is released, thereby enhancing safety.
2. In the electric vehicle control system disclosed in Japanese Patent Laid-Open No. 80202 of 1982, a microcomputer is reset once if a current flowing into a dc motor is higher than a voltage is signal corresponding to the position of an accelerator pedal. After a predetermined time, operation of the motor is restarted.
However, these prior art devices involve the following problems:
Prior art 1 provides inferior driving performance because the acceleration and regeneration of the main circuit are turned off whenever the accelerator is released in ordinary driving.
Prior art 2, on the other hand, resets the microcomputer, but does not interrupt the current itself in the event of a malfunction of the microcomputer; thus, the vehicle continues running while the microcomputer is reset. Also, it may occur that the microcomputer must be reset repeatedly if it is not recovered from the malfunction, which is also a safety hazard.
In view of the foregoing, it is an object of the present invention to provide an electric vehicle control system which offers good driving performance in ordinary driving, and can securely cut off current upon malfunction of a microcomputer before restarting.